Mission: Purple Polyurethane Bushings to Improve Car Handling

Can you improve your car’s handling and precision by replacing your stock rubber bushings with polyurethane bushings? That’s what this project is all about. Our mission is to install a full set of polyurethane bushes in our Miata and find out.

The bushings, or bushes, are the rubber bits holding all the moving parts in your car’s suspension system. They hold everything in place and provide pivot points for all your suspension’s moving parts. From control arms to wishbones to anti-roll bars, wherever there is a moving part, there is a bushing in that joint to aid in keeping things together and to encourage movement in the correct direction.

Stock bushings in vehicles are made out of natural rubber. Natural rubber is soft and pliable. This is nice at first, because it’s generally comfortable and precise enough. But over time, rubber breaks down and gets softer. This in turn equates to more slop and degraded handling. It can also cause other moving parts to wear out more quickly – such as tires.

This is one of the reasons a new car feels so much better than a car that’s only a couple of years old. Cars that are even older, like 10 years plus, not only have worn out bushings but they are likely cracked and rotten too. This makes for a huge part of the crappy feel a very old car has when driven.

A project like this could be considered for the following reasons:

1. The stock rubber bushings in your car are worn out and could definitely benefit from replacing.
2. The stock rubber bushings in your car are actually in OK shape, but you just want to upgrade.

So what are we doing? We’re taking our 1995 RallyWays Miata and replacing all the stock rubber bushes with brand new polyurethane units. Then we’re telling you about the results.

Upon doing the research for this project we found that along with improved handling, car enthusiasts’ biggest concerns with polyurethane bushings is: Noise, vibrations and harshness – Otherwise referred to as (NVH). At any time you hear us mention NVH, you know we’re talking about the noise, vibration and harshness associated with the ride quality of your car.

Of course, harshness can can be rather subjective. What’s tolerable for some might not be for others. What we definitely don’t want however is a bunch of noise and squeaks. For this reason, we have been researching our choice of bushings very thoroughly.

We don’t like to mess about when it comes to major projects. We believe it’s always best to start with the best quality products regardless of price. The “you get what you pay for” adage fits perfectly here as it does in most cases.

Upon researching the market and what’s available we turned to PowerFlex USA to supply the bushings for our project car.

There are a few reasons why we chose PowerFlex. First of all, PowerFlex has been around for quite a while and has been making waves in BMW enthusiast circles. Secondly, upon looking at their product we could tell the quality is there. Plus, the bushings are purple. Come on. How can you pass that up? Purple.

There’s more however. Our project car is the RallyWays Mazda Miata. As many of you know, the answer is always Miata. If it works for this little car, it will most likely be perfect for any other situation. Also, upon searching through Miata message boards all over the web, we haven’t found concrete information yet on PowerFlex bushes installed in a Miata. All the projects we have been able to find so far on Miatas have been from other bushing manufacturers. And well, the results seem to be all over the place. Some love. Some hate. We’re not about to say that other bushing makers are putting forth so-so product, and thus our Miata friends are all unhappy. No. We can only speak from our own experience and we’re not about to tear into our Miata and install every bushing from every bushing maker to try them out. They’re not exactly as easy to change and test as tires.

For this reason, we’ve picked a bushing maker from the lot believing the quality is there and we’re testing them out.

Here are some things to note

PowerFlex bushings come in three flavors based on durometer (how hard they are):

Yellow – Soft, but still harder than rubber. Durometer: 70A
Purple – Medium hardness. What we’re using. Durometer: 80A
Black – Really hard. Typically for track use. Durometer: 95A

For those of you that grew up skating, you know exactly what those durometer numbers mean. They are all very similar numbers to the durometers used for polyurethane wheels and bushings for skateboards and longboards.

While our entire kit is mostly purple, we did receive a set of black bushings – This was the package for the Miata’s rear lower outer wishbone bush. We were a bit puzzled at first as to why. Upon contacting PowerFlex USA, the very tech-savvy Carrie Stike told us that for that specific application, the harder black bushings have proven to be a better choice.

Like we said earlier, we’re not working with cheap parts here. A full set of bushings for Mazda Miata will run you around $600, give or take. Of course, this will vary a bit from car to car. Also, you don’t really have to replace ALL your bushings. You can balance a project out based on a few selections or only replace stock bushings that have fully worn out. The important thing is to balance the install from side to side – in other words, what you do on the left of the car, also do on the right.

However, since we’re tearing the entire suspension apart, we decided to might as well replace all of them.

We basically selected every PowerFlex product available on this page of miata bushings, with the exception of the front and rear anti-roll bar bushings. We are replacing the stock anti-roll bars in our Miata in the near future anyway and the aftermarket units already come with polyurethane bushings. Plus, being thicker bars, the stock sized PowerFlex bushings wouldn’t fit the new bars anyway.

We also selected 4 exhaust mounts for our Miata. These are actually red. While the stock rubber exhaust mounts on our car are in perfect shape, we’ve been complaining about rattle from our exhaust system. We’re hoping the stiffer PowerFlex exhaust hanger mounts will hold the exhaust system in place a little better. More on that as well.

The appearance of the product has us super excited to get these on our car. Each bushing looks like a quality product. The shape is flawless and the finish of each bushing is perfectly clean. There is no excess material and we couldn’t find any imperfections from the molds either.

The quality of the PowerFlex USA units was evident even in the packaging. Each set of bushings is packed in a very nice translucent clear, purple and yellow plastic box that looks great and is easy to open and close. They turned out to be more than just boxes as it has made it super easy to keep our batch of bushings organized even after opening them up to inspect them. Every package is clearly labelled to help you make sure what each set of bushings is for (upper wishbone inner, upper wish bone outer, lower wishbone inner, outer, etc). This is pretty good news for shop owners as well. At point of purchase, these would make the job of selling bushings a lot easier.

What’s even more cool and exudes a whiff of extra quality and reassurance is that every single package was individually labelled by the person that packaged it. One read, “Picked and Packed by Terry.” Another read, “Picked and Packed by Inam.” Seeing this tells you a lot of care went into making sure we got all the right bushings for our project. The last thing you want is to have your car at the shop or on jack stands in your garage only to find out you got the wrong parts.

So far, we’re quite confident in our choice of PowerFlex to upgrade the bushings our project Miata.

Another thing to keep in mind is that upon inspecting our car, the stock bushes actually seem fine. The only cracked and old-looking bushings we could find were those of the end links for the stock sway bars. Those we’re replacing separately. However, for an 18 year old car, the stock rubber bushings seem fine – at least by looks alone. On the other hand, they are natural rubber. Yes, the car only has 64,000 miles, but there’s no way 18-year-old rubber can still be fresh. Plus, we can tell the vagueness and imprecision of the steering and handling of this car when compared to our 2011 Mazda MX-5 Miata NC – The NC is much more precise, has no slop in the steering and it transmits more road and steering feedback. We’re hoping the bushing upgrade can help our little NA Miata achieve the precision our newer car has.

What’s more important here is that this isn’t simply a Miata project. The results we achieve here would translate perfectly to other cars. Not to mention, PowerFlex makes bushings for a full host of car brands and models. And like we said earlier, we’re pretty confident putting these in our Miata. Checking out the BMW forums, the feedback on PowerFlex seems to be a lot more positive than what the Miata guys are saying from using other bushing makers to supply parts for their cars.

The technical aspect of this project, mainly the installation process will be run in our Miata specialty section of RallyWays. Keep an eye there for the installation articles. You can also subscribe to the Miata specialty section to get updates directly to your inbox. Subscription is free. Just make sure to select to receive the Miata Specialty articles when you join.

Note however, we will publish another story here on the main blog with the results after the installation and testing. Until next time… RW